Semiconductor devices are used in a large number of electronic devices, such as computers, cell phones, and others. Semiconductor devices comprise integrated circuits that are formed on semiconductor wafers by depositing many types of thin films of material over the semiconductor wafers, and patterning the thin films of material to form the integrated circuits. Integrated circuits typically include field-effect transistors (FETs).
Conventionally, planar FETs have been used in integrated circuits. However, with the ever increasing density and decreasing footprint requirements of modern semiconductor processing, planar FETs may generally incur problems when reduced in size. When using high-k dielectric material in the gate structure, the high-k dielectric material cannot be easily formed on the semiconductor substrate. An interfacial layer between the high-k dielectric layer and the semiconductor substrate allows better capacitance contribution, integrity and quality of the high-k dielectrics. However, the interfacial layer is often a thick oxide layer on the channel region of the FETs. The resulting gate stack has a thickness that renders the device dimension overly sized.